Radiation
Natural Radiation on Mars is much higher compared with Earth. The thin atmosphere provides only a small shielding effect against harmful solar radiation and cosmic radiation.
Danger
The harmful radiation causes cancer. There is no such thing as a limit, below which the radiation dose is harmless. Small dose - small risk of cancer. High dose - high risk of cancer.
Nevertheless, there are defined legal limits for exposure during work for several professional activities, such as for X-ray assistants, airplane personnel, etc.
Protection
Houses should be equipped with a shielding, thick enough to reduce the radiation to a level equal to Earth, that is almost zero. Best protection may be achived with houses built in natural caves.
Space suits should reduce the radiation as much as possible, considering the additional weigth to bear. According to the protection class of the suit type the dose of radiation per hour is different and should be considered for planning.
